package com.peak.spring.boot.tools;


public class IdWorker {

	private long workerId;

	private long datacenterId;

	private long sequence = 0L;

	private long twepoch = 1446789857406l;

	private long workerIdBits = 5L;

	private long datacenterIdBits = 5L;

	private long maxWorkerId = -1L ^ (-1L << workerIdBits);

	private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);

	private long sequenceBits = 12L;

	private long workerIdShift = sequenceBits;

	private long datacenterIdShift = sequenceBits + workerIdBits;

	private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;

	private long sequenceMask = -1L ^ (-1L << sequenceBits);

	private long lastTimestamp = -1L;

	public IdWorker(long workerId, long datacenterId) {
		// sanity check for workerId
		if (workerId > maxWorkerId || workerId < 0) {
			throw new IllegalArgumentException(
					String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
		}
		if (datacenterId > maxDatacenterId || datacenterId < 0) {
			throw new IllegalArgumentException(
					String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
		}
		this.workerId = workerId;
		this.datacenterId = datacenterId;
	}
	public synchronized long nextId() {
		long timestamp = timeGen();
		if (timestamp < lastTimestamp) {
			throw new RuntimeException(String.format(
					"Clock moved backwards. Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
		}
		if (lastTimestamp == timestamp) {
			sequence = (sequence + 1) & sequenceMask;
			if (sequence == 0) {
				timestamp = tilNextMillis(lastTimestamp);
			}
		} else {
			sequence = 0L;
		}
		lastTimestamp = timestamp;
		return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
	}

	protected long tilNextMillis(long lastTimestamp) {
		long timestamp = timeGen();
		while (timestamp <= lastTimestamp) {
			timestamp = timeGen();
		}
		return timestamp;
	}

	protected long timeGen() {
		return System.currentTimeMillis();
	}

	public static void main(String[] args) throws InterruptedException {
		IdWorker worker = new IdWorker(2, 1);
		for (int i = 0; i < 50; i++) {
			System.out.println(Thread.currentThread().getName() + "=" + worker.nextId());
		}
	}
}
